A string of code from iOS 7 revealing 'a fingerprint that changes colour during the setup process' was posted online yesterday, sparking rumours that the new iPhone could contain a fingerprint sensor.

If the rumours are true, the latest iPhone will be the first Apple product to feature such a sensor, which could be used for unlocking the homescreen or confirming identity for payment from the App Store or other outlets. Any sensor would likely be embedded into the physical home button.

Earlier this year it was reported that a supply chain source in Taiwan said Apple had been forced to delay production of the next iPhone due to failure to find a coating material that did not interfere with the fingerprint sensor.

Fingerprint sensors have not been widely utilised across smartphones in the past. Motorola released the Atrix 4G in 2011 which featured a biometric fingerprint sensor it claimed offered a level of security surpassing password or PIN locks. Customers reported mixed levels of success with the scanner, with many saying the sensor failed to recognise their fingerprint. Other digital security systems include the Samsung Galaxy S3's Face Unlock feature, also available on Google's Nexus 4, and in the future it's likely phones will unlock upon recognition of its owner's voice.

Last year Apple purchased mobile and network security company AuthenTec for $356m, which produces hardware including fingerprint sensors, fuelling further speculation about the sensor's introduction into future Apple products.

The latest iPhone is expected to be released in September, though it is still unknown whether it will be known as the iPhone 5S or iPhone 6. Apple is also believed to be near to announcing the release of a 'budget' iPhone designed to target the emerging smartphone markets in China and India. The model is likely to feature a plastic interface instead of aluminium, and could retail for as little as $99.

Other rumoured features of the next model include an A7 processor, heightened Siri voice recognition facilities and an improved camera system.